Ion Irradiation Effects on Ho_{2+<i>_x</i>}Ti_{2-<i>_x</i>}O<sub>7-<i>_x</></i>/2 (x=0, 0.4 and 0.67)

Abstract

We recently synthesized different composition polycrystalline Ho2+xTi2-xO7-x/2 (x=0, 0.4 and 0.67), which is derivative fluorite compounds known as and pyrochlore phases in Ho3O2-TiO2 phase diagram by using conventional solid state synthesis methods. The samples were irradiated with 400 keV Ne2+ ions at cryogenic temperature (~77 K), using the Danfysik ion accelerator at the Ion Beam Materials Laboratory (IBML) of Los Alamos National Laboratory (LANL). The irradiation fluences in the experiments ranged from 5×1014-5×1015ions/cm2. An order-to-disorder (O-D) transformation was observed for α, β and pyrochlore phases, as determined using grazing incidence X-ray diffraction (GIXRD) at an incident angle of 0.25°. The O-D transformation threshold fluence for α phase was found to be noticeably lower than those for β phase and pyrochlore, and the O-D transformation threshold fluence for β phase was the highest. The O-D transformation threshold fluence was found to be coherent with the phase transformation temperature in the Ho3O2-TiO2temperature-composition (T-C) phase diagram.